1. Field of the Invention
The present invention relates to a mechanical ignition sensor for sensing a state of a sudden deceleration of a vehicle or the like.
2. Description of the Related Art
As a seat belt system mounted to a vehicle, there is known, for example, one provided with a so-called pretensioner wherein a webbing applied to an occupant is retracted a predetermined amount when the vehicle suddenly decelerates. The looseness of the webbing applied to the occupant is thus forcibly removed so as to tighten the webbing to thereby improve occupant-restraining characteristics.
With this type of pretensioner, there is known one wherein a take-up shaft of a webbing retractor is forcibly rotated so as to tighten a webbing and one wherein a buckle is forcibly pulled so as to tighten a webbing. For example, the latter pretensioner is provided with a gas generator having a mechanical ignition sensor. A cylinder is attached to the gas generator and coupled to a buckle via a wire or the like.
When the vehicle suddenly decelerates, a state of a sudden deceleration is detected by the mechanical ignition sensor and the gas generator is operated to instantaneously generate gas. As a result, the cylinder which generated the gas is moved and the resultant moving force is transmitted to the buckle via the wire so as to forcibly move the buckle, thereby tightening the webbing.
The mechanical ignition sensor employed in such pretensioner basically comprises an ignition pin for igniting a detonator, an inertial body, which is inertially moved by a large acceleration, and a trigger member, which is interposed between the ignition pin and the inertial body so as to prevent the ignition pin from moving. Further, a safety device is provided thereat for preventing a malfunction of the mechanical ignition sensor when the sensor is assembled to the vehicle or the like.
The safety device includes a safety lever, which engages the inertial body moved by the inertial force and prevents the movement of the inertial body regardless of the operation of the inertial force. When the safety lever engages the inertial body, the movement of the inertial body is forcibly prevented as described above. Accordingly, even if external force is unnecessarily applied to the vehicle when the safety lever is assembled thereto, the malfunctioning of the sensor is prevented.
The safety device (the safety lever) of the conventional mechanical ignition sensor having the aforementioned structure must be reliably operated, and the operation thereof must be smoothly and reliably performed. For example, to confirm sensitivity and other operational properties of the mechanical ignition sensor and to test reliability of the operation, the operation test is performed by temporarily setting the sensor to an operative state (a state in which the safety device is released) by the operation of the safety lever. Then, when the sensor is properly assembled to the gas generator, the sensor must be set to an inoperative state (a state in which the safety device is operating) by the operation of the safety lever. Namely, the safety lever provided at the mechanical ignition sensor must be reliably operated between the state in which it is operating and the state in which it is released, and the operation thereof must be performed smoothly.
After the conventional safety device (the safety lever) is temporarily released, it is difficult to set the device to the operative state (the state in which the sensor is inoperative). Also, the operation of the conventional device is complicated and cannot be Smoothly performed. Therefore, there is a room for improvement, and a solution to this problem has been desired.
On the other hand, due to a structure of a webbing retractor provided with a pretensioner, that of a buckle device or the mounting direction of the mechanical ignition sensor with respect to the vehicle, the conventional mechanical ignition sensor having the above structure is structured for exclusive use with either a left-hand side occupant seat or a right-hand side occupant seat of the vehicle.
Namely, the directions of relative movement of the inertial body, for example, are different (opposite) between the mechanical ignition sensor for the left-hand side occupant seat and the one for the right-hand side occupant seat. Consequently, the inertial body as well as the aforementioned safety device (the safety lever), which prevents the movement of the inertial body, is also structured for exclusive use with either the left-hand side occupant seat or the right-hand side occupant seat. As a result, parts for the mechanical ignition sensor were prevented from being used in common by the left-hand side occupant seat and the right-hand side occupant seat. The range over which the parts can be applied was hindered from being increased.
Further, the safety device (the safety lever) of such mechanical ignition sensor must be reliably operated and the operation thereof must be smoothly and reliably performed. For example, to confirm sensitivity and other operational properties of the mechanical ignition sensor and to test reliability of the operation, the operation test is performed by temporarily setting the sensor to an operative state (the state in which the safety device is released) by the operation of the safety lever. Then, when the sensor is properly assembled to the gas generator, the sensor must be set to an inoperative state (the state in which the safety device is operating) by the operation of the safety lever. Namely, the operation of the safety lever provided at the mechanical ignition sensor must be performed smoothly and reliably.